The present invention relates to the field of golf clubs and in particular, to the driver or number 1 wood used for tee shots.
A persistent problem, which is worse for golfers of high handicaps, is failure to hit the golf ball fully on the club strike face. The hits are sometimes partly off and even entirely off the face, with consequent extremely bad effects on the distance and accuracy of the hit. There are practical limits to enlarging the club strike face to reduce this problem. This fault of having the ball partially off the club face at impact is much less common with low handicap golfers, but it does happen now and then. For them, a small improvement is relatively as important as a large improvement is for a high handicap golfer.
A study was undertaken to determine if the typical shape of the face was reasonably suited to the typical pattern of hits on the face. The impact of a driver on a golf ball flattens the ball and leaves a circular contact area about 0.7 inch diameter or greater, with a standard golf ball. The center of this circular contact area will be referred to as the center of impact. An analysis was made of 11 hits by each of 28 golfers, with a driver, a 5-iron, and a 9-iron. The club strike face was covered with marking tape which marked the impact area and the locations of the centers of each of the impacts was measured and recorded. The study showed that there was a pronounced elliptical distribution pattern of impacts over that many swings, and we call this pattern the "hit pattern". Further, it was found that for drivers this elliptical pattern was rotated upward at the toe about 32 degrees.
The study showed that the driver faces were not oriented to take advantage of the shape of the hit patterns and the present invention relates to tilting the long axis of the outline of the face upward at the toe of a driver to cause a better match with the hit pattern. Enlarging the face is also helpful as stated, but when the face is enlarged and also tilted appropriately, the improvement is much enhanced.
In most prior art, commercially available driver face shapes have only a small amount of upward tilt and none appears to have nearly the tilt angle which minimized the percentage of hits which were off of the face (or partly off the face).
In U.S. Pat. No. 3,625,518 a driver is disclosed as having a curved bottom surface and in the disclosure an elliptical representation of the hit area is shown. The minor axis of the hit area is recited as being parallel to the club shaft axis and the patent disclosure calls for a bulge on the face to be formed about an axis parallel to the minor axis of the hit area to compensate for off center impact. The face surface is also rolled about an axis parallel to the long axis of the ellipse. Thus while the elliptical ball strike region is known in the prior art the solution for using this information to adapt the club head tilt to aid golfers was not recognized.
U.S. Pat. No. 4,471,961 illustrates an axis of rotation in FIG. 17 but does not indicate that orienting the club face to be tilted upward toward the toe will aid in insuring the ball will be hit on the club face. This patent is also concerned with the bulge and roll of the driver face.
A prior club that had a circular face is known to have been sold in about 1990. Since it was circular it had no long axis and the idea of rotation of its long axis has no meaning. Its shape is much different from the approximate ratio of length to width of 2, which is a ratio appropriate to match the hit pattern and is widely preferred.